Speaking in Florida, Mr Glenn said that he is ready to relive the journey.

He told journalists: "I have been pleasantly surprised at the outpouring of interest in this flight. And it's really gratifying to see people get so fired up about this space programme again and about their interest in it."

Glenn: Making history in 1962

During his nine days in space, Glenn will be a medical guinea pig, taking part in than 80 experiments.

Apart from the US crew, Discovery will also be carrying a Japanese researcher and a European Space Agency astronaut from Spain.

Ready for lift-off

Pointing toward space at the Cape Canaveral launch site, the shuttle Discovery now stands ready for take-off.

Officials say final preparations are going smoothly, but the launch will depend on the weather.

Nasa meteorologists are keeping a close watch on Hurricane Mitch in the Caribbean.

Although the powerful storm was moving away from Florida, forecasters were concerned it might build up strength by Thursday's launch.

Hurricane could stall plans

However, Nasa says plans are in place in case the storm fails to co-operate.

Nasa test director Doug Lyons: "The most likely option is that we would make two consecutive attempts and then stand down for a 96-hour period.